1. Field of the Invention
This invention generally relates to a rear derailleur for a bicycle. More specifically, the present invention relates to an adjusting mechanism for adjusting the position of the chain guide in an axial direction with respect to a multistage sprocket assembly of the bicycle.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. One part of the bicycle that has been extensively redesigned is the drive train of the bicycle.
Most of today""s bicycles are multi-speed bicycles that allow the rider to select the appropriate gear ratio to suit the particular riding conditions encountered during the bicycle ride. One of the most popular types of gearing assemblies for multi-speed bicycles utilize a chain extending between a set of front sprockets mounted for rotation with the pedals and a set of rear sprockets mounted on the rear hub of the rear bicycle wheel for rotation therewith. Two derailleurs are typically used to move the chain between the sprockets or gears. Generally, most derailleurs (front or rear derailleurs) include a fixed or base member secured to a bicycle frame, and a movable member with a chain guide that is supported for movement relative to the fixed or base member by a linkage assembly. The chain guide has a pair of guide plates that form a chain receiving slot for contacting and moving a chain between the sprockets.
In the case of a rear derailleur, the chain guide has a pair of pulleys that are rotatably mounted between the guide plates. Also the base member in a rear derailleur is supported swingably to the bicycle frame through a horizontal shaft or axle, and the chain guide is swingably mounted to the movable member through a horizontal shaft or axle. A spring is interposed between the movable member and the chain guide for applying tension to the chain guide. The base member is fixed to a fork end of the bicycle frame, with the chain guide being disposed radially outwardly of the multistage sprocket assembly.
When the rider operates the shift operating device of the front derailleur shifting mechanism, the operating conduit or cable pulls the front derailleur such that the chain is moved outwardly from one gear or sprocket to the next gear or sprocket, or releases the front derailleur such that the chain is moved inwardly from one gear or sprocket to the next gear or sprocket. Likewise, when the rider operates the shift operating device of the rear derailleur shifting mechanism, the operating conduit or cable pulls the rear derailleur such that it moves the chain inwardly from one gear or sprocket to the next inner gear or sprocket, or releases the rear derailleur such that it moves the chain outwardly from one gear or sprocket to the next gear or sprocket. In other words, when the shift operating devices are moved to release the derailleur, the front derailleur will move inwardly towards the center of the bicycle, while the rear derailleur will move outwardly away from the center of the bicycle.
The conventional derailleur which includes a chain guide capable of being adjusted in its axial position with respect to the multistage sprocket assembly is well-known as disclosed in U.S. Pat. No. 4,850,940 to Nagano and assigned to Shimano, Inc. Specifically, Shinano""s prior U.S. Pat. No. 4,850,940 shows an adjusting mechanism for a chain guide which has a housing or movable member non-rotatably mounted on a tubular member via an adjusting screw. The tubular member is coupled to the chain guide via a fixing pin and bushing. A spring is disposed inside the tubular member to rotationally bias the tubular member and housing. The housing has an outer cylindrical portion that is slidable on the tubular member. The housing is not coupled to the fixing pin. Because the outer cylindrical portion is sized to slide on the tubular member and the housing is not coupled to the fixing pin, some play or looseness exists between these members. Also, due to this looseness, the housing can vibrate on the tubular member. Such vibrations can cause the adjusting screw to rotate undesirably. Such rotation of the adjusting screw can allow the chain guide to be out of alignment with the free wheel sprockets.
Therefore, it is desirable to have an adjustment mechanism with a housing that eliminates the play or looseness between the housing and the tubular member. Providing a housing that has an inner cylindrical portion that is slidable on the fixing pin can eliminate this looseness. It is also desirable to provide an adjusting screw that will not rotate undesirably due to vibrations.
In view of the above, there exists a need for derailleur which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
One object of the present invention is to provide all adjusting mechanism for a rear derailleur that has less play than adjusting mechanisms of the prior art.
Another object of the present invention is to provide an adjusting mechanism for a rear derailleur that is easy to assemble.
Another object of the present invention is to provide an adjustment mechanism for a rear derailleur that has an anti-loosening mechanism.
The foregoing objects of the present invention can basically be attained by providing an adjusting mechanism for adjusting a position of a chain guide of a bicycle derailleur in an axial direction. The adjusting mechanism basically comprises an axle, a housing, a fixed element, a biasing member and an adjustment member operatively coupled between said housing and said fixed element to movably support said housing in an axial direction on said axle. The axle has a first end and a second end. The housing has an attachment portion and a first tubular guide portion. The attachment portion is adapted to be coupled to a linkage assembly of the bicycle derailleur. The first tubular guide portion is pivotally coupled to the first end of the axle. The fixed element has a second tubular guide portion that is coupled to the second end of the axle. The second tubular guide portion extends from the fixed element and is coaxially arranged around the first tubular guide portion. The biasing member is positioned between the first and second tubular guide portions and arranged to urge the housing relative to the fixed element in a rotational direction about the axle.
The foregoing objects of the present invention can basically be attained by providing a derailleur for a bicycle with an adjusting mechanism for adjusting a position of a chain guide of a bicycle derailleur in an axial direction. The derailleur basically comprises a base member, a movable member with a chain guide and a linkage assembly. The base member is arranged to be coupled to a part of the bicycle and pivotally supported on a first axle with a fixed element. The movable member is adapted to shift a chain of the bicycle in a transverse direction. The movable member is pivotally supported on a second axle that is coupled to a plate element of the chain guide. The linkage assembly is movably coupled between the base member and the movable member to move the chain guide between a retracted position and an extended position. Either the base member or the movable member has an adjusting mechanism for movably supporting it in an axial direction on a corresponding first or second axle. The adjusting mechanism has a first tubular guide portion extending from the selected member to pivotally engage the corresponding first or second axle. A second tubular guide portion extends from the selected element and is coaxially arranged around the first tubular guide portion. A biasing member is positioned between the first and second tubular guide portions and arranged to urge the selected member relative to the selected element in a rotational direction about the corresponding axle. An adjustment member is operatively coupled between the selected member and the selected element.
In a preferred embodiment, a derailleur comprises a base member, a movable member with a chain guide and a linkage assembly. The base member is arranged to be coupled to a part of the bicycle and pivotally supported on a first axle with a fixed element. The movable member is adapted to shift a chain of the bicycle in a transverse direction. The movable member is pivotally supported on a second axle that is coupled to the chain guide. The linkage assembly is movably coupled between the base member and the movable member to move the chain guide between a retracted position and an extended position. In one embodiment, the movable member has an adjusting mechanism that movably supports said movable member in an axial direction on the second axle. The adjusting mechanism basically includes a first tubular guide portion extending from the movable member to pivotally engage the second axle, a second tubular guide portion extending from the chain guide and arranged around the first tubular guide portion, a biasing member positioned between the first and second tubular guide portions and arranged to urge the movable member relative to chain guide in a rotational direction about the second axle, and an adjustment member operatively coupled between the movable member and the chain guide. In another embodiment, the base member has an adjusting mechanism that movably supports the base member in an axial direction on the first axle.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.